This application relates generally to a locking mechanism for selectively preventing the rotation of a rotatable shaft. More particularly, this application relates to a locking mechanism for selectively preventing the rotation of a rotatable shaft within a rotary power tool, allowing for easier installation of accessories to the rotary tool.
Rotary tools are well known, and they are generally comprised of a motor coupled to at least one rotatable shaft, a tool holder or chuck coupled to the shaft, and a switch mechanism for selectively turning the motor on or off. In many rotary tools, a directional control is also coupled to the motor, in order to selectively control the direction in which the motor rotates the shaft. Drill bits or other attachments are received and secured by the chuck, enabling the rotary tool to be customized to perform a variety of different applications.
One problem common with a number of rotary tools involves securing drill bits or other attachments to the chuck. Typically, the chuck has a cavity in which the attachment is received and jaws surrounding the cavity to secure the attachment within the chuck. The jaws are positionable to secure or release an attachment by rotating the chuck about the shaft. However, since the shaft is typically freely rotatable when the drill is not activated, rotating the chuck about the shaft becomes quite difficult unless the shaft is locked in place while the chuck is rotated.
There are various mechanisms currently used to lock the shaft in place during tool attachment. A common mechanism for locking the shaft in place includes the use of a key which is attached to the chuck during the insertion or removal of an attachment. Disadvantages in these keyed chucks include the fact that the keys are easily lost or misplaced, and that they are often cumbersome to use. Some tools use a two-sleeve keyless chuck to insert or remove attachments to the rotary tool. Such keyless chucks often require the user to hold one sleeve to resist rotation of the shaft with one hand, while turning the chuck with the other. The two-sleeve keyless chuck has the disadvantage of needing two hands to operate. Also, the grip areas on each sleeve are typically small so that it is often difficult to generate sufficient torque to secure an attachment. Other rotary tools have complex mechanisms coupled to the trigger of the rotary tool, these mechanisms preventing the rotation of the shaft when the drill is not activated. Disadvantages in these devices may include a degradation of the drive motor due to the locking mechanism and the added expense of implementing the locking mechanism within the rotary tool.
While these and other methods may work for their intended purposes, significant improvement and innovation in a rotary tool design can still be achieved by the creation of a locking mechanism which is easy to activate and of simple design.
Therefore, it is a general object of this application to provide a power tool with a locking mechanism which avoids the disadvantages of prior designs, while affording additional structural and operating advantages.
An important feature is the provision of a tool of the type set forth which is of simple construction and relatively economical to implement.
Another important feature is the provision of a rotary tool that avoids the accidental activation of the tool while the shaft is in the locking position.
Another important feature is the provision of a rotary power tool with a shaft locking mechanism which is easily activated.
A still further feature is the provision of a tool of the type set forth which minimizes the locking force required.